I believe the '70 vintage LT-1 engine came equipped with a unique valve cover breather element, which is found on the same side as the oil fill. How hard/rare is this original part to find, and what is it's fair price? Also, can you recommend the right supplier? Many thanks, Jeff Burkey
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Re: '70 LT-1 valve cover breather element
Jeff----
If there was any special "breather element" used on 1970 LT-1 engines, I have no recollection of it whatsover. The engine oil fill was located on the left side valve cover rear, as I recall. The PCV valve was fitted to a rubber grommet located on the front half of the left side valve cover. The right side valve cover, as I recall, had the Corvette crossed-flag emblem on the front portion and a rubber grommet, identical to the PCV grommet, on the rear portion. As part of the PCV system, an "L"-shaped tube fitted into the grommet and connected to a short length of rubber tubing which connected to a fitting on the base of the open-element air cleaner. The air cleaner base had a wire mesh flame arrestor at the outlet of this fitting.
If you are talking about the baffle assembly which is located beneath the rubber grommets in the valve covers, the design of these units did change at least three times over the course of the production of these valve covers in an attempt to improve oil control. However, these baffles, or "breathers" if you will, were an integral part of the valve cover, were never available as a seperate service part, and cannot be easily replaced or serviced.
I'll do a little research this evening to see if there's something I'm missing here but, that's how I recall it.In Appreciation of John Hinckley -
Re: '70 LT-1 valve cover breather element
You may need to clarify your terminology a little.
1970 LT1 as well as earlier and later Chevolet engines used a Positive Crankcase Ventilation (PCV) system with an enclosed crank case. There is no crankcase breather vent when a PCV system is used. The carburetor creates a vacuum that, under most engine operating conditions, draws crankcase vapors into the intake manifold. Fresh air is supplied to the crankcase through a rubber tube that connects to the air filter.
Terry
TerryComment
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Re: '70 LT-1 valve cover breather element
The left side valve cover towards the front of the engine has the opening for the PCV, which is connected via rubber hose to the intake. At the other end of this valve cover is the crossed flag emblem. On the right side valve cover towards the front of the engine is the screw-type cover for the oil fill. At the other end of this side is another opening for a "device", I thought a breather cap of some type. Is this what you are suggesting needs to connect back to the air breather element via the flame arrestor opening at the base of the air filter? If so, what is this part and where can it be located, if it is important for proper engine performance? Many thanks! Jeff BurkeyComment
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Re: '70 LT-1 valve cover breather element
Jeff,
First off it, sounds like your valve covers are reversed. The oil fill cap is on the Left (drivers side) toward the rear of the cover. There is a smaller opening in the front of the left cover, with a gromet in it. The PCV valve fits in that gromet.
On the right (passengger) side at the rear is a small hole with a gromet that has a right angle fittling that connects to a hose that goes into the air cleaner base. At the front of the right hand cover is the crossed flag label.
Original covers have no hole under that label, but some replacements have an opening for an oil fill cap (thus the same replacement cover can be used on either side) under that label. Original covers were different for right and left.
Hope this helps.
Terry
TerryComment
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Re: '70 LT-1 valve cover breather element
Jeff,
While taking a second look at this I realized I failed to answer part of your question.
The proper connection of this system is important to the operation of your engine. The carburetor is designed for the amount of air that is supplied through the PCV valve. The mixture will be off if there is no PCV valve connected, or if the wrong PCV valve is used.
Also the vapors that are in the crankcase need to be vented in some fashon. If they are allowed to build without proper venting the crankcase pressure will cause oil leaks at the pan, valve covers and a lot of other places.
It is wise to properly configure the PCV system. I believe most, if not all, the parts of this simple system are still available from Chevrolet.
Terry
TerryComment
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Re: '70 LT-1 valve cover breather element
Jeff----
I totally agree with Terry that you should properly restore the PCV system for your car; these systems were marginal, at best, for providing for proper crankcase ventilation but, without them in place, you're in for real trouble and especially the oil leaks that Terry spoke about.
As Terry mentioned, most of the parts that you need are still available from GM and at very modest cost. The PCV valve is GM# 6484525(AC/Delco CV-746C); the valve cover grommets are GM #3989348; the connector(metal tube from valve cover grommet to air cleaner) is GM #3868842, and the short connector hose is GM #3932336. The molded PCV hose from the carburetor base to the left valve cover is also still available but your GM dealer counterman won't find it in any Corvette parts catalog; they'll tell you that it's unavailable or use generic fuel line. The GM part number for this hose is 3981058; you will only need to cut the long end to fit and that's VERY easy. Unfortunately, the wire-mesh-like flame arrestor which is found inside the air cleaner base at the PCV tube inlet, GM #3849856, is discontinued. I believe that you can get these in reproduction(if you need it-yours might still be there)from the like of Paragon, etc.In Appreciation of John HinckleyComment
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Re: '70 LT-1 valve cover breather element
Joe, a short note to say "thank you" for your diligent research and helpful commentary with regards to my question on the breather element for the '70 LT-1. I have taken your advice and ordered the correct parts to re-install the correct crankcase ventilation system. Jeff BurkeyComment
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Re: '70 LT-1 valve cover breather element
Joe, a short note to say "thank you" for your diligent research and helpful commentary with regards to my question on the breather element for the '70 LT-1. I have taken your advice and ordered the correct parts to re-install the correct crankcase ventilation system. Jeff BurkeyComment
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